U.S. patent application number 10/992909 was filed with the patent office on 2005-06-09 for shaped articles from cycloaliphatic polyester compositions.
Invention is credited to McWilliams, Douglas Stephens, Mercer, James Wilson JR., Shelby, Marcus David, Tincher, Mark Elliott.
Application Number | 20050124779 10/992909 |
Document ID | / |
Family ID | 34710055 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050124779 |
Kind Code |
A1 |
Shelby, Marcus David ; et
al. |
June 9, 2005 |
Shaped articles from cycloaliphatic polyester compositions
Abstract
Disclosed are oriented, shaped articles such as, for example,
film, fibers, bottles, and tubes, with excellent strength,
toughness, clarity, chemical resistance, and UV resistance. The
articles can be prepared from cycloaliphatic polyesters and from
compositions comprising cycloaliphatic polyesters and
cycloaliphatic polyester elastomers. The articles may be oriented
by stretching in at least one direction and have a modulus which
results in a soft feel. Also disclosed are polyester compositions
comprising cycloaliphatic polyesters and polyester elastomers.
Inventors: |
Shelby, Marcus David;
(Kingsport, TN) ; McWilliams, Douglas Stephens;
(Kingsport, TN) ; Mercer, James Wilson JR.;
(Kingsport, TN) ; Tincher, Mark Elliott;
(Kingsport, TN) |
Correspondence
Address: |
ERIC D. MIDDLEMAS
EASTMAN CHEMICAL COMPANY
P. O. BOX 511
KINGSPORT
TN
37662-5075
US
|
Family ID: |
34710055 |
Appl. No.: |
10/992909 |
Filed: |
November 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60527097 |
Dec 4, 2003 |
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Current U.S.
Class: |
528/206 |
Current CPC
Class: |
C08L 67/025 20130101;
C08L 67/02 20130101; Y10T 428/1397 20150115; C08J 5/18 20130101;
Y10T 428/13 20150115; Y10T 428/31507 20150401; C08L 67/02 20130101;
Y10T 428/1352 20150115; C08J 2367/02 20130101; C08L 67/025
20130101; Y10T 428/31504 20150401; C08L 2666/18 20130101; C08K
5/0041 20130101; C08K 5/005 20130101; C08L 2666/18 20130101 |
Class at
Publication: |
528/206 |
International
Class: |
C08G 063/06 |
Claims
We claim:
1. A shaped article, comprising: i. about 5 to 100 weight percent,
based on the total weight of said article, of a cycloaliphatic
polyester comprising about 98 to about 100 mole %, based on the
total mole % of diacid residues, of residues of at least one diacid
selected from the group consisting of 1,3-cyclohexanedicarboxylic
acid and 1,4-cyclohexanedicarboxylic acid; and about 70 to about
100 mole %, based on the total mole % of diol residues, of residues
of at least one diol selected from the group consisting of
1,3-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol,
and 1,4-cyclohexanedimethanol; and ii. 0 to about 95 weight percent
of a polyester elastomer; wherein said article is oriented by
stretching in at least one direction.
2. The shaped article according to claim 1 wherein said diol
residues further comprise 0 to about 30 mole %, based on the total
diol residues, of residues of at least one diol selected from the
group consisting of: ethylene glycol, 1,2-propanediol,
1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
1,8-octanediol, 1,10-decanediol, neopentyl glycol, and
2,2,4-trimethyl 1,3-pentanediol.
3. The shaped article according to claim 2 wherein said at least
one diacid is 1,4-cyclohexanedicarboxylic acid.
4. The shaped article according to claim 3 wherein said diol
residues comprise about 95 to 100 mole %, based on the total diol
residues, of residues of 1,4-cyclohexanedimethanol.
5. The shaped article according to claim 1 wherein said polyester
is poly(1,3 cyclohexylenedimethylene-1,3-cyclohexanedicarboxylate),
poly(1,4 cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate), or
poly(2,2,4,4-tetramethyl-1,3-cyclobutylene-1,4-cyclohexanedicarboxylate)
6. The shaped article according to claim 1 wherein said polyester
elastomer comprises: i. diacid residues comprising residues of one
or more diacids selected from the group consisting of substituted
or unsubstituted, linear or branched aliphatic dicarboxylic acids
containing 2 to 20 carbon atoms, substituted or unsubstituted,
linear or branched cycloaliphatic dicarboxylic acids containing 5
to 20 carbon atoms, and substituted or unsubstituted aromatic
dicarboxylic acids containing 6 to 20 carbon atoms; and ii. diol
residues comprising residues of one or more substituted or
unsubstituted, linear or branched, diols selected from the group
consisting of aliphatic diols containing 2 to 20 carbon atoms,
poly(oxyalkylene)glycols and copoly(oxyalkylene)glycols having an
average molecular weight of about 400 to about 12000,
cycloaliphatic diols containing 5 to 20 carbon atoms, and aromatic
diols containing 6 to 20 carbon atoms.
7. The shaped article according to claim 6 wherein said diacid
residues of said polyester elastomer comprise residues of at least
one diacid selected from the group consisting of
1,4-cyclohexanedicarboxylic acid; 1,3-cyclohexanedicarboxylic acid;
terephthalic acid; isophthalic acid; sodiosulfoisophthalic acid;
adipic acid; glutaric acid; succinic acid; azelaic acid; dimer
acid; and 2,6-naphthalenedicarboxylic acid.
8. The shaped article according to claim 7 wherein said diol
residues of said polyester elastomer comprise residues of at least
one diol selected from the group consisting of ethylene glycol;
1,3-propanediol; 1,4-butanediol; 1,5-pentanediol;
2-methylpropanediol; 2,2-dimethylpropanediol; 1,6-hexanediol;
decanediol; 2,2,4,4-tetramethyl-1,3-cyclobutanediol;
1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol; poly(ethylene
ether)glycol; poly(propylene ether)glycol; and poly(tetramethylene
ether) glycol.
9. The shaped article according to claim 8 wherein said polyester
elastomer further comprises residues of one or more branching
agents having 3 or more functional groups wherein said functional
groups are hydroxyl, carboxyl, or a combination thereof.
10. The shaped article according to claim 9 wherein said polyester
elastomer comprises at least 90 mole %, based on the total moles of
diacid residues, of residues of at least one diacid selected from
the group consisting of 1,4-cyclohexanedicarboxylic acid and
terephthalic acid; about 2 to about 30 mole %, based on the total
diol residues, of a poly(tetramethylene ether) glycol having an
average molecular weight of about 400 to about 2000, and about 98
to about 70 mole %, based on the total diol residues, of residues
of at least one diol selected from the group consisting of
1,4-cyclohexanedimethanol and 1,4-butanediol; and about 0.1 to
about 2 mole %, based on the total diacid residues, of residues of
at least one branching agent selected from the group consisting of
trimellitic acid, trimellitic anhydride, and pyromellitic
dianhydride.
11. The shaped article according to claim 10 wherein said polyester
elastomer comprises at least 95 mole %, based on the total moles of
diacid residues, of residues of 1,4-cyclohexanedicarboxylic acid;
and about 98 to about 70 mole %, based on the total diol residues,
of residues of 1,4-cyclohexanedimethanol.
12. The shaped article according to claim 5 or 11 wherein said
article comprises about 5 to about 95 wt % of said cycloaliphatic
polyester and about 5 to about 95 wt % of said polyester
elastomer.
13. The shaped article according to claim 12 wherein said
cycloaliphatic polyester is poly(1,4
cyclohexylenedimethylene-1,4-cyclohexanedicarboxyla- te).
14. The shaped article according to claim 10 or 11 wherein said
article comprises about 30 to about 100 weight percent of said
cycloaliphatic polyester and 0 to 70 weight percent of said
polyester elastomer, based on the total weight of said article.
15. The shaped article according to claim 14 wherein said article
comprises about 90 to about 100 weight percent of said
cycloaliphatic polyester and 0 to 10 weight percent of said
polyester elastomer, based on the total weight of said article.
16. The shaped article according to claim 14 wherein said article
comprises about 30 to about 50 weight percent of said
cycloaliphatic polyester and 50 to 70 weight percent of said
polyester elastomer, based on the total weight of said article.
17. The shaped article according to claim 9 further comprising at
least one additive selected from the group consisting of hindered
amine light stabilizers, UV absorbers, optical brighteners, and
oxidative stabilizers.
18. The shaped article according to claim 11 which has a
birefringence of at least 0.01.
19. The shaped article according to claim 18 wherein said article
is a bottle, film, sheet, profiles, fiber, tube, or molded
article.
20. The shaped article according to claim 19 wherein said article
is heatset.
21. The shaped article according to claim 19 wherein said article
is microvoided.
22. The shaped article according to claim 19 wherein said article
is a shrink film.
23. The shaped article according to claim 19 or 20 wherein said
article is a biaxially oriented film.
24. The shaped article according to claim 19 wherein said article
comprises one or more layers.
25. The shaped article according to claim 24 wherein said article
comprises a plurality of layers, wherein at least one layer has a
thickness of 1 .mu.m or less.
26. The shaped article according to claim 19 wherein said article
is a fiber.
27. The shaped article according to claim 26 wherein said fiber is
a staple, monofilament, or multifilament fiber having a shaped
cross-section.
28. A shaped article, comprising: i. about 30 to 100 weight
percent, based on the total weight of the article, of a
cycloaliphatic polyester comprising about 98 to about 100 mole %,
based on the total mole % of diacid residues, of residues of
1,4-cyclohexanedicarboxylic acid; and about 90 to about 100 mole %,
based on the total mole % of diol residues, of residues of
1,4-cyclohexanedimethanol; and ii. 0 to about 70 weight percent of
an polyester elastomer comprising least 90 mole %, based on the
total moles of diacid residues, of residues of at least one diacid
selected from the group consisting of 1,4-cyclohexanedicarboxylic
acid and terephthalic acid; about 2 to about 30 mole %, based on
the total diol residues, of a poly(tetramethylene ether) glycol
having an average molecular weight of about 400 to about 2000, and
about 98 to about 70 mole % of residues of at least one diol
selected from the group consisting of 1,4-cyclohexanedimethanol and
1,4-butanediol; and about 0.1 to about 2 mole %, based on the total
diacid residues, of residues of at least one branching agent
selected from the group consisting of trimellitic acid, trimellitic
anhydride, and pyromellitic dianhydride; wherein said article is
oriented by stretching in at least one direction.
29. The shaped article according to claim 28 wherein said article
comprises about 90 to about 100 weight percent of said
cycloaliphatic polyester and 0 to 10 weight percent of said
polyester elastomer, based on the total weight of said article.
30. The shaped article according to claim 28 wherein said article
comprises about 30 to about 50 weight percent of said
cycloaliphatic polyester and 50 to 70 weight percent of said
polyester elastomer, based on the total weight of said article.
31. The shaped article according to claim 28 further comprising one
or more of: hindered amine light stabilizers, UV absorbers, optical
brighteners, or oxidative stabilizers.
32. The shaped article according to claim 28 wherein said article
is a bottle, film, sheet, profiles, fiber, tube, or molded
article.
33. The shaped article according to claim 32 wherein said article
is heatset.
34. The shaped article according to claim 32 wherein said article
is a shrink film.
35. The shaped article according to claim 32 or 33 wherein said
article is a biaxially oriented film.
36. A polyester composition, comprising: i. about 20 to about 80
weight percent, based on the total weight of the composition, of a
cycloaliphatic polyester comprising about 98 to about 100 mole %,
based on the total mole % of diacid residues, of residues of one or
more of diacids selected from the group consisting of
1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic
acid; and about 70 to about 100 mole %, based on the total mole %
of diol residues, of residues of one or more diols selected from
the group consisting of 1,3-cyclohexanedimethanol,
2,2,4,4-tetramethyl-1,3-cyclobutanediol, and
1,4-cyclohexanedimethanol; and ii. 20 to about 80 weight percent of
a polyester elastomer; wherein said composition at 25.degree. C.
has a storage modulus of at least 0.3 GPa and a tan delta of at
least 0.02.
37. The polyester composition according to claim 36 consisting
essentially of: i. about 30 to about 80 weight percent, based on
the total weight of said composition, of a cycloaliphatic polyester
consisting essentially of about 98 to about 100 mole %, based on
the total mole % of diacid residues, of residues of
1,4-cyclohexanedicarboxylic acid; and about 90 to about 100 mole %,
based on the total mole % of diol residues, of residues of
1,4-cyclohexanedimethanol; and ii. about 20 to about 70 weight
percent of a polyester elastomer consisting essentially of least 90
mole %, based on the total moles of diacid residues, of residues of
1,4-cyclohexanedicarboxylic acid or terephthalic acid; about 2 to
about 30 mole %, based on the total diol residues, of a
poly(tetramethylene ether) glycol having an average molecular
weight of about 400 to about 2000, and about 98 to about 70 mole %
of residues of 1,4-cyclohexanedimethanol or 1,4-butanediol; and
about 0.1 to about 2 mole %, based on the total diacid or diol
residues, of residues of trimellitic acid, trimellitic anhydride,
or pyromellitic dianhydride.
38. The polyester composition according to claim 36 which comprises
about 30 to about 50 weight percent of said cycloaliphatic
polyester and 50 to 70 weight percent of said polyester elastomer,
based on the total weight of said article.
39. The polyester composition according to claim 36 wherein said
diacid residues comprise residues of 1,4-cyclohexanedicarboxylic
acid.
40. The polyester composition according to claim 39 wherein said
diol residues comprise residues of 1,4-cyclohexanedimethanol.
41. The polyester composition according to claim 40 wherein said
tan delta is at least 0.05 and said storage modulus is at least 0.5
GPa.
42. The polyester composition according to claim 37 further
consisting essentially of one or more of: hindered amine light
stabilizers, UV absorbers, optical brighteners, or oxidative
stabilizers.
43. A shaped article comprising the polyester composition of claim
37 wherein said article is a bottle, film, sheet, profile, fiber,
tube, or molded object.
44. The shaped article according to claim 43 wherein said article
is heatset.
45. The shaped article according to claim 43 wherein said article
is a shrink film.
46. The shaped article according to claim 43 or 44 wherein said
article is a biaxially oriented film.
47. The shaped article according to claim 43 wherein said article
comprises one or more layers.
48. The shaped article according to claim 47 wherein said article
comprises a plurality of layers, wherein at least one layer has a
thickness of 1 .mu.m or less.
49. A process for a polyester composition, comprising mixing: i.
about 20 to about 80 weight percent, based on the total weight of
the article, of a cycloaliphatic polyester comprising about 98 to
about 100 mole %, based on the total mole % of diacid residues, of
residues of one or more diacids selected from the group consisting
of 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic
acid; and about 70 to about 100 mole %, based on the total mole %
of diol residues, of residues of one or more diols selected from
the group consisting of 1,3-cyclohexanedimethanol,
2,2,4,4-tetramethyl-1,3-cyclobutanediol, and
1,4-cyclohexanedimethanol; and ii. about 20 to about 80 weight
percent of a polyester elastomer; wherein said composition at
25.degree. C. has a storage modulus of at least 0.3 GPa and a tan
delta of at least 0.02.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/527,097 filed Dec. 4, 2003.
FIELD OF THE INVENTION
[0002] This invention pertains generally to oriented, shaped
articles prepared from cycloaliphatic polyesters and compositions
comprising cycloaliphatic polyesters and polyester elastomers. More
specifically, this invention pertains to oriented, shaped articles
such as, for example, bottles, films, sheets, profiles, fibers,
tubes, and molded objects prepared from cycloaliphatic polyesters
or compositions comprising cycloaliphatic polyesters and polyester
elastomers. The invention further pertains to cycloaliphatic
polyester compositions comprising a polyester elastomer.
BACKGROUND OF THE INVENTION
[0003] Polyesters are often used to manufacture shaped articles for
use in a wide range of applications, including films, sheets,
profiles, bottles, and the like. The most commonly used polyesters
are based on terephthalic or isophthalic acid monomers and include,
for example, poly(ethylene terephthalate) ("PET"),
poly(1,4-butylene terephthalate) ("PBT"),
poly(cyclohexylenedimethylene terephthalate) ("PCT"), and their
copolyesters. These polyesters are inexpensive, widely available
and, because of their aromatic content, have a high glass
transition temperature (Tg), which gives a shaped article thermal
resistance, stiffness (i.e. modulus) and toughness. Recently, much
of the emphasis in the polyester arts has been to develop
polyesters with higher glass transition temperatures by
incorporating greater aromaticity into the polymer (e.g. liquid
crystal polyesters, PEN). For certain applications, however, these
aromatic polyesters are not acceptable, particularly those
applications in which the article requires UV or chemical
resistance, good light transmission, and/or a "soft feel". The term
"soft feel" refers to tactile properties similar to those found in
polyolefins in which the material is soft to the touch, but still
retains structural integrity, elasticity and resiliency. For
example, shaped articles prepared from these aromatic polyesters
often require a protective cap layer to guard against UV and
chemical exposure. In addition, the high modulus of aromatic
polyesters makes them unacceptable for use in soft-feel and "low
noise" applications, except where a high level of plasticizer is
added.
[0004] By contrast, aliphatic and cycloaliphatic polyesters
typically have good UV and chemical resistance and a lower modulus
in comparison to aromatic polyesters. These polyesters, however,
have undesirably low glass transition temperatures making them
unfit for many applications. For example, many aliphatic and
cycloaliphatic type polyesters have glass transition temperatures
below room temperature which results in an excessively soft and
rubbery polymer with little or no structural integrity. In
contrast, aliphatic and cycloaliphatic polyesters with glass
transition temperatures above room temperature are glassy but lack
adequate toughness and thermal resistance in comparison to aromatic
polyesters because their Tg is still too low. Thus, shaped articles
prepared from aliphatic and cycloaliphatic polyesters are often
inadequate for many applications such as, for example, wall
coverings, fibers, packaging, labels, and soft films. Some examples
of various cycloaliphatic polyester compositions and their
applications are described in U.S. Pat. Nos. 5,306,785; 5,859,119;
5,907,026; 6,011,124; 5,486,562; 5,907,026; 4,665,153; 6,084,055;
6,455,664; and 6,136,441; U.S. patent application Publication No.
2003/0030172 A1; European Patent Application No. 0 902 052 A1; and
in PCT Application No.'s WO 93/04124 and WO 02/31020 A2.
[0005] Other non-aromatic polyesters do not cure these deficiencies
and present additional shortcomings when used for shaped articles.
For example, polyester elastomers such as, for example, PCCE
copolyesterethers (a copolymer of 1,4-cyclohexanedicarboxylic acid,
1,4-cyclohexanedimethanol, and polytetramethylene glycol (available
under the trademark ECDEL.RTM. polyester from Eastman Chemical
Company) have many desirable properties, such as the toughness and
UV/chemical resistance mentioned above. They also have a soft feel,
but are too soft and rubbery, and lack the thermal resistance
needed to be used in many structural applications. Furthermore,
because of these rubber-like properties in combination with their
slow crystallization characteristics, extruded films and fibers
from these polyester elastomers tend to stick to take up rolls or
spinning guides during extrusion. Fluoropolymer and matte
rolls/tooling tend to alleviate the sticking problem but such
materials are expensive and require dedicated processing lines.
Thus, it would be desirable to prepare shaped articles such as, for
example, bottles, films, sheets, profiles, fibers, tubes, and
molded objects, that have good UV and chemical resistance while
simultaneously retaining strength, toughness, thermal resistance,
and soft feel characteristics. Such articles would have
applications in wall coverings, bottles, soft films, packaging,
labels, and fibers.
SUMMARY OF THE INVENTION
[0006] We have unexpectedly discovered that oriented shaped
articles having chemical and UV resistance with excellent strength,
toughness, and clarity may be prepared from cycloaliphatic
polyesters and compositions comprising cycloaliphatic polyesters
with polyester elastomers. Our invention thus provides a shaped
article, comprising:
[0007] i. about 5 to 100 weight percent, based on the total weight
of the article, of a cycloaliphatic polyester comprising about 98
to about 100 mole %, based on the total mole % of diacid residues,
of the residues of at least one diacid selected from the group
consisting of 1,3-cyclohexanedicarboxylic acid and
1,4-cyclohexanedicarboxylic acid; and about 70 to about 100 mole %,
based on the total mole % of diol residues, of the residues of at
least one diol selected from the group consisting of
1,3-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobut-
anediol, and 1,4-cyclohexanedimethanol; and
[0008] ii. 0 to about 95 weight percent of a polyester
elastomer;
[0009] wherein the article is oriented by stretching in at least
one direction.
[0010] Examples of oriented, shaped articles in accordance with our
invention are films, sheets, fibers, bottles, profiles, tubes, and
molded objects.
[0011] The shaped articles may be prepared entirely from a
cycloaliphatic polyester such as, for example, polyesters in which
about 98 to about 100 mole % of the diacid residues comprise one or
more residues of 1,3- or 1,4-cyclohexanedicarboxylic acid and in
which about 70 to about 100 mole % of the diol residues comprise
one or more residues of a cycloaliphatic diol such as, for example,
1,3-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol,
and 1,4-cyclohexanedimethanol. Alternatively, the shaped articles
may be prepared from compositions comprising a cycloaliphatic
polyester and a polyester elastomer. For example, the shaped
article may comprise from about 5 to about 95 weight % (wt %)
cycloaliphatic polyesters and about 5 to about 95 wt % of a
polyester elastomer. In one embodiment, the polyester elastomer is
also a cycloaliphatic polyester comprising at least 95 mole %,
based on the total moles of diacid residues, of the residues of
1,4-cyclohexanedicarboxylic acid; about 98 to about 70 mole %,
based on the total diol residues, of the residues of
1,4-cyclohexanedimethanol, and about 2 to about 30 mole %, based on
the total diol residues, of a poly(tetramethylene ether) glycol
having an average molecular weight of about 400 to about 2000. The
cycloaliphatic polyester and polyester elastomer may further
comprise a branching agent to provide additional stiffness and
improve melt processing characteristics of the polyester
composition. The cycloaliphatic polyesters and polyester elastomers
are naturally miscible, which helps to improve orientation and
toughness characteristics of the shaped articles produced
therefrom.
[0012] One example of a shaped article of the instant invention is
a film, which may be monoaxially or biaxially oriented. The shaped
article may be a shrink film or may be heatset to provide
dimensional stability. It may be microvoided or foamed to reduce
the overall density. The shaped article also may comprise one or
more layers and, in one embodiment, may comprise a plurality of
thin layers wherein at least one layer has a thickness of 1 .mu.m
or less. Such multilayer shaped articles exhibit light-altering
effects such as, for example, polarization and selective filtering
of light (e.g. iridescent films). In another example, the shaped
article of the invention may also be a staple, monofilament, or
multifilament fiber having shaped cross-section.
[0013] The present invention also provides a polyester composition,
comprising:
[0014] i. about 20 to 80 weight percent, based on the total weight
of the composition, of a cycloaliphatic polyester comprising about
98 to about 100 mole %, based on the total mole % of diacid
residues, of the residues of one or more of diacids selected from
the group consisting of 1,3-cyclohexanedicarboxylic acid and
1,4-cyclohexanedicarboxylic acid; and about 70 to about 100 mole %,
based on the total mole % of diol residues, of the residues of one
or more diols selected from the group consisting of
1,3-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobut-
anediol, and 1,4-cyclohexanedimethanol; and
[0015] ii. 20 to about 80 weight percent of a polyester
elastomer;
[0016] wherein said composition at 25.degree. C. has a storage
modulus of at least 0.3 GPa and a tan delta of at least 0.02.
[0017] This composition also may be used for the preparation of
shaped articles as described above which, in turn, may be oriented
or unoriented. In yet another aspect, the invention provides a
process for the preparation of the above composition.
DETAILED DESCRIPTION
[0018] It has been found that certain copolyesters, particularly
cycloaliphatic polyesters and/or compositions of these polyesters
with certain polyester elastomers containing one or more hard
segments and one or more polyether or polyester-ether soft segments
are useful for the preparation of oriented shaped articles that
have a combination of properties such as, for example, strength,
toughness, soft feel, chemical resistance, thermal resistance and
UV resistance. Thus, in a general embodiment, the present invention
provides a shaped article, comprising: (i) about 5 to 100 weight
percent, based on the total weight of the article, of a
cycloaliphatic polyester comprising about 98 to about 100 mole %,
based on the total mole % of diacid residues, of the residues of at
least one diacid selected from the group consisting of
1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic
acid; and about 70 to about 100 mole %, based on the total mole %
of diol residues, of the residues of at least one diol selected
from the group consisting of 1,3-cyclohexanedimethanol,
2,2,4,4-tetramethyl-1,3-cyclobut- anediol, and
1,4-cyclohexanedimethanol; and (ii) 0 to about 95 weight percent of
a polyester elastomer; wherein the article is oriented by
stretching in at least one direction. Representative examples of
the shaped articles of the invention include, but are not limited
to, bottles, films, sheets, profiles, fibers, tubes, and molded
objects. Such articles have broad applications in wall coverings,
soft films, packaging, labels, and fibers.
[0019] Unless otherwise indicated, all numbers expressing
quantities of ingredients, properties such as molecular weight,
reaction conditions, and so forth used in the specification and
claims are to be understood as being modified in all instances by
the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the following specification
and attached claims are approximations that may vary depending upon
the desired properties sought to be obtained by the present
invention. At the very least, each numerical parameter should at
least be construed in light of the number of reported significant
digits and by applying ordinary rounding techniques. Further, the
ranges stated in this disclosure and the claims are intended to
include the entire range specifically and not just the endpoint(s).
For example, a range stated to be 0 to 10 is intended to disclose
all whole numbers between 0 and 10 such as, for example 1, 2, 3, 4,
etc., all fractional numbers between 0 and 10, for example 1.5,
2.3, 4.57, 6.1113, etc., and the endpoints 0 and 10. Also, a range
associated with chemical substituent groups such as, for example,
"C.sub.1 to C.sub.5 hydrocarbons", is intended to specifically
include and disclose C.sub.1 and C.sub.5 hydrocarbons as well as
C.sub.2, C.sub.3, and C.sub.4 hydrocarbons.
[0020] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
inherently contains certain errors necessarily resulting from the
standard deviation found in their respective testing
measurements.
[0021] The term "polyester", as used herein, is intended to include
"copolyesters" and is understood to mean a synthetic polymer
prepared by the polycondensation of one or more difunctional
carboxylic acids with one or more difunctional hydroxyl compounds.
The term "cycloaliphatic polyester", as used herein, means a
polyester comprising a molar excess of the residues of
cycloaliphatic dicarboxylic acids and/or cycloaliphatic diols.
"Cycloaliphatic" as used herein with respect to the diols and
dicarboxylic acids of the invention, refers to structures which
contain as a backbone a cyclic arrangement of the constituent
carbon atoms which may be saturated or paraffinic in nature,
unsaturated, i.e., containing non-aromatic carbon-carbon double
bonds, or acetylenic, i.e., containing carbon-carbon triple bonds.
Typically, the difunctional carboxylic acid is a dicarboxylic acid
and the difunctional hydroxyl compound is a dihydric alcohol such
as, for example, glycols and diols.
[0022] In the present invention, the difunctional carboxylic acid
typically is a cycloaliphatic dicarboxylic acid such as, for
example, 1,4-cyclohexanedicarboxylic acid, and the difunctional
hydroxyl compound may be cycloaliphatic diol such as, for example,
1,4-cyclohexanedimethano- l. The term "residue", as used herein,
means any organic structure incorporated into a polymer through a
polycondensation reaction involving the corresponding monomer. The
term "repeating unit", as used herein, means an organic structure
having a dicarboxylic acid residue and a diol residue bonded
through a carbonyloxy group. Thus, the dicarboxylic acid residues
may be derived from a dicarboxylic acid monomer or its associated
acid halides, esters, salts, anhydrides, or mixtures thereof. As
used herein, therefore, the term dicarboxylic acid is intended to
include dicarboxylic acids and any derivative of a dicarboxylic
acid, including its associated acid halides, esters, half-esters,
salts, half-salts, anhydrides, mixed anhydrides, or mixtures
thereof, useful in a polycondensation process with a diol to make a
high molecular weight polyester.
[0023] The cycloaliphatic polyesters used in the present invention
typically are prepared from dicarboxylic acids and diols which
react in substantially equal proportions and are incorporated into
the polyester polymer as their corresponding residues. The
cycloaliphatic polyesters of the present invention, therefore,
contain substantially equal molar proportions of acid residues (100
mole %) and diol residues (100 mole %) such that the total moles of
repeating units is equal to 100 mole %. The mole percentages
provided in the present disclosure, therefore, may be based on the
total moles of acid residues, the total moles of diol residues, or
the total moles of repeating units. For example, a polyester
containing 30 mole % 1,4-cyclohexane dicarboxylic acid (1,4-CHDA),
based on the total acid residues, means that the polyester contains
30 mole % 1,4-CHDA residues out of a total of 100 mole % acid
residues. Thus, there are 30 moles of 1,4-CHDA residues among every
100 moles of acid residues. In another example, a polyester
containing 30 mole % 1,4-cyclohexanedimethanol (1,4-CHDM), based on
the total diol residues, means that the polyester contains 30 mole
% 1,4-CHDM residues out of a total of 100 mole % diol residues.
Thus, there are 30 moles of 1,4-CHDM residues among every 100 moles
of diol residues.
[0024] The polyester composition comprises about 5 to 100 weight
percent of a cycloaliphatic polyester. The cycloaliphatic polyester
comprises about 98 to about 100 mole percent (abbreviated herein as
"mole %"), based on the total diacid residues, of the residues of
at least one diacid selected from the group consisting of
1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic
acid. For example, the diacid may be 1,4-cyclohexanedicarboxylic
acid. The 1,3- and 1,4-cyclohexanedicarboxyli- c acids may be used
as their pure cis or trans isomers or as a mixture of cis and trans
isomers. Cycloaliphatic acids having a high level of trans isomers
(greater than 60 mole % trans) are generally preferred to provide
higher glass transition temperatures.
[0025] The cycloaliphatic polyester of our invention also contains
diol residues that may comprise about 70 to about 100 mole % of at
least one reside selected from 1,3-cyclohexanedimethanol,
2,2,4,4-tetramethyl-1,3-c- yclobutanediol, and
1,4-cyclohexanedimethanol (abbreviated herein as "CHDM"). As used
herein, the term "diol" is synonymous with the term "glycol" and
means any dihydric alcohol. As with the diacids, cis, trans, and
mixtures of cis, trans isomers of the glycols are intended to be
included within the scope of the invention. For example, CHDM may
be used as the pure cis or trans isomer or as a mixture of cis,
trans isomers. High levels of trans isomers are generally preferred
as described above for the diacids. In addition to cycloaliphatic
diols, the cycloaliphatic polyester may also comprise and lesser
amounts of aliphatic diols. For example, the cycloaliphatic
polyester may comprise 0 to about 30 mole %, based on the total
moles of diol residues, of the residues of at least one diol
selected from of linear or branched, aliphatic diols containing 2
to about 16 carbon atoms. Typical examples of diols include
ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol,
neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol,
2,2,4-trimethyl 1,3-pentanediol, and the like. In another example,
the diol residues of the polyester may comprise about 95 to about
100 mole %, based on the total diol residues, of the residues of
1,4-cyclohexanedimethanol. In a further example, the diacid may be
1,4-cyclohexanedicarboxylic acid and, in another example, the diol
may be 1,4-cyclohexanedimethanol. In yet another example, the
cycloaliphatic polyester may be poly(1,3
cyclohexylenedimethylene-1,3-cyclohexanedicarbo- xylate), poly(1,4
cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate), or
poly(2,2,4,4-tetramethyl-1,3-cyclobutylene-1,4-cyclohexanedicarboxylat-
e).
[0026] Although not essential to the invention, the cycloaliphatic
polyester may comprise up to 2 mole percent, based on the total
moles of diol or diacid residues, of the residues of one or more
branching agents having 3 or more carboxyl substituents, hydroxyl
substituents, ionic forming groups, or a combination thereof, to
improve melt strength and processability. Examples of branching
agents include, but are not limited to, multifunctional acids or
glycols such as trimellitic acid, trimellitic anhydride,
pyromellitic dianhydride, trimethylolpropane, glycerol,
pentaerythritol, citric acid, tartaric acid, 3-hydroxyglutaric acid
and the like. Examples of ionic forming groups include
sodiosulfoisophthalic acid and sodiosulfobenzoic acid. In one
example, the branching agent residues comprise about 0.1 to about 1
mole percent of one or more residues of: trimellitic anhydride,
pyromellitic dianhydride, glycerol, sorbitol, 1,2,6-hexanetriol,
pentaerythritol, trimethylolethane, or trimesic acid. The branching
agent may be added to the polyester reaction mixture or blended
with the polyester in the form of a concentrate as described, for
example, in U.S. Pat. Nos. 5,654,347.
[0027] The polyesters of the present invention have an inherent
viscosity of about 0.5 to about 1.5 dL/g. The inherent viscosity,
abbreviated herein as "I.V.", refers to inherent viscosity
determinations made at 25.degree. C. using 0.25 gram of polymer per
50 mL of a solvent composed of 60 weight percent phenyl and 40
weight percent tetrachloroethane. Other examples of I.V. values
which may be exhibited by the polyester compositions are about 0.6
to about 1.2 dL/g, about 0.7 to about 1.1 dL/g.
[0028] The shaped article also comprises from 0 to about 95 wt % of
a polyester elastomer. The term "polyester elastomer", as used
herein, is understood to mean any polyester having a low modulus of
about 1 to 500 megaPascals (MPa) (at room temperature) which easily
undergoes deformation and exhibits reversible elongations under
small applied stresses, i.e., elasticity. By the term "reversible",
as used herein, it is meant that the polyester returns to its
original shape after any applied stress is removed. In general,
these are prepared by conventional esterification/polycondensation
processes from (i) one or more diols, (ii) one or more dicarboxylic
acids, (iii) one or more long chain ether glycols, and optionally,
(iv) one or more lactones or polylactones. For example, the
polyester elastomer of the present invention may comprise (i)
diacid residues comprising the residues of one or more diacids
selected from substituted or unsubstituted, linear or branched
aliphatic dicarboxylic acids containing 2 to 20 carbon atoms,
substituted or unsubstituted, linear or branched cycloaliphatic
dicarboxylic acids containing 5 to 20 carbon atoms, and substituted
or unsubstituted aromatic dicarboxylic acids containing 6 to 20
carbon atoms; and (ii) diol residues comprising the residues of one
or more substituted or unsubstituted, linear or branched, diols
selected from aliphatic diols containing 2 to 20 carbon atoms,
poly(oxyalkylene)-glycols and copoly(oxyalkylene)glycols having an
average molecular weight of about 400 to about 12000,
cycloaliphatic diols containing 5 to 20 carbon atoms, and aromatic
diols containing 6 to 20 carbon atoms. Representative dicarboxylic
acids which may be used to prepare the polyester elastomer include,
but are not limited to, 1,4-cyclohexanedicarboxylic acid;
1,3-cyclohexanedicarboxylic acid; terephthalic acid; isophthalic
acid; sodiosulfoisophthalic acid; adipic acid; glutaric acid;
succinic acid; azelaic acid; dimer acid;
2,6-naphthalenedicarboxylic acid, and mixtures thereof. Preferred
aliphatic acids include 1,4-cyclohexanedicarboxylic acid, sebacic
acid, dimer acid, glutaric acid, azelaic acid, adipic acid, and
mixtures thereof. Cycloaliphatic dicarboxylic acids such as, for
example, 1,4-cyclohexanedicarboxylic acid may be present as the
pure cis or trans isomer or as a mixture of cis and trans isomers.
Preferred aromatic dicarboxylic acids include terephthalic,
phthalic and isophthalic acids, sodiosulfoisophthalic, and
2,6-naphthalenedicarboxylic acid, and mixtures thereof.
[0029] The polyester elastomer also may comprise the residues of at
least one diol. Examples of diols include ethylene glycol;
1,3-propanediol; 1,4-butanediol; 1,5-pentanediol;
2-methylpropanediol; 2,2-dimethylpropanediol; 1,6-hexanediol;
decanediol; 2,2,4,4-tetramethyl-1,3-cyclobutanediol;
1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol; poly(ethylene
ether)glycol; poly(propylene ether)glycol; and poly(tetramethylene
ether) glycol. For example, the polyester elastomer may comprise
the residues of a poly(oxyalkylene) glycol such as, for example, a
poly(tetramethylene ether) glycol having an average molecular
weight of about 400 to about 2000 Although not required, the
polyester elastomer may comprise the residues of a branching agent
having 3 or more carboxyl substituents, hydroxyl substituents, or a
combination thereof. Examples of branching agents include, but are
not limited to, multifunctional acids or glycols such as
trimellitic acid, trimellitic anhydride, pyromellitic dianhydride,
trimethylolpropane, glycerol, pentaerythritol, citric acid,
tartaric acid, 3-hydroxyglutaric acid and the like. Examples of
branching agent levels within the polyester elastomer are about 0.1
to about 2 mole %, about 0.1 to about 1 mole % and 0.5 to about 1
mole %, based on the total moles of diacid or diol residues.
[0030] In a further embodiment, the polyester elastomers of the
present invention may comprise at least 90 mole %, based on the
total moles of diacid residues, of the residues of at least one
diacid selected from 1,4-cyclohexanedicarboxylic acid and
terephthalic acid; about 2 to about 30 mole %, based on the total
diol residues, of a poly(tetramethylene ether) glycol having an
average molecular weight of about 400 to about 2000, and about 98
to about 70 mole %, based on the total diol residues, of the
residues of at least one diol selected from the group consisting of
1,4-cyclohexanedimethanol and 1,4-butanediol; and about 0.1 to
about 2 mole %, based on the total diacid residues, of the residues
of at least one branching agent selected from the group consisting
of trimellitic acid, trimellitic anhydride, and pyromellitic
dianhydride. In yet another example, the polyester elastomer also
may comprise at least 95 mole %, based on the total moles of diacid
residues, of the residues of 1,4-cyclohexanedicarboxylic acid; and
about 98 to about 70 mole %, based on the total diol residues, of
the residues of 1,4-cyclohexanedimethanol. Examples of commercially
available polyester elastomers which may be used in the polyester
composition of the present invention include ECDEL.RTM. polyester
elastomers (available from Eastman Chemical Company) and
HYTREL.RTM. polyester elastomers (available from DuPont Company).
In some cases, it may be desirable to use mixtures of the
HYTREL.RTM. and ECDEL.RTM. polyester elastomers with the
cycloaliphatic polyester.
[0031] In addition, the polyester elastomers may have incorporated
therein one or more lactones or polylactones. Lactones suitable
herein are widely available commercially, e.g., Union Carbide
Corporation and Aldrich Chemicals. While epsilon caprolactone is
especially preferred, it is also possible to use substituted
lactones wherein the lactone is substituted by a lower alkyl group
such as a methyl or ethyl group at the alpha, beta, gamma, delta,
or epsilon positions. Additionally, it is possible to use
polylactone, including homopolymers and copolymers thereof with one
or more components, as well as hydroxy terminated polylactone, as
block units in these poly(ether esters).
[0032] The polyesters and the polyester elastomers of the instant
invention are readily prepared from the appropriate dicarboxylic
acids, esters, anhydrides, or salts, the appropriate diol or diol
mixtures, and optional branching agents using typical
polycondensation reaction conditions. They may be made by
continuous, semi-continuous, and batch modes of operation and may
utilize a variety of reactor types. Examples of suitable reactor
types include, but are not limited to, stirred tank, continuous
stirred tank, slurry, tubular, wiped-film, falling film, or
extrusion reactors. The term "continuous" as used herein means a
process wherein reactants are introduced and products withdrawn
simultaneously in an uninterrupted manner. By "continuous" it is
meant that the process is substantially or completely continuous in
operation in contrast to a "batch" process. "Continuous" is not
meant in any way to prohibit normal interruptions in the continuity
of the process due to, for example, start-up, reactor maintenance,
or scheduled shut down periods. The term "batch" process as used
herein means a process wherein all the reactants are added to the
reactor and then processed according to a predetermined course of
reaction during which no material is fed or removed into the
reactor. The term "semicontinuous" means a process where some of
the reactants are charged at the beginning of the process and the
remaining reactants are fed continuously as the reaction
progresses. Alternatively, a semicontinuous process may also
include a process similar to a batch process in which all the
reactants are added at the beginning of the process except that one
or more of the products are removed continuously as the reaction
progresses. The process is operated advantageously as a continuous
process for economic reasons and to produce superior coloration of
the polymer as the polyester may deteriorate in appearance if
allowed to reside in a reactor at an elevated temperature for too
long a duration.
[0033] The cycloaliphatic polyesters and polyester elastomers of
the present invention are prepared by procedures known to persons
skilled in the art. The reaction of the diol, dicarboxylic acid,
and optional branching agent components may be carried out using
conventional polyester polymerization conditions. For example, when
preparing the cycloaliphatic polyester or polyester elastomer by
means of an ester interchange reaction, i.e., from the ester form
of the dicarboxylic acid components, the reaction process may
comprise two steps. In the first step, the diol component and the
dicarboxylic acid component, such as, for example, dimethyl
terephthalate, are reacted at elevated temperatures, typically,
about 150.degree. C. to about 250.degree. C. for about 0.5 to about
8 hours at pressures ranging from about 0.0 kPa gauge to about 414
kPa gauge (60 pounds per square inch, "psig"). Preferably, the
temperature for the ester interchange reaction ranges from about
180.degree. C. to about 230.degree. C. for about 1 to about 4 hours
while the preferred pressure ranges from about 103 kPa gauge (15
psig) to about 276 kPa gauge (40 psig). Thereafter, the reaction
product is heated under higher temperatures and under reduced
pressure to form the polyester with the elimination of diol, which
is readily volatilized under these conditions and removed from the
system. This second step, or polycondensation step, is continued
under higher vacuum and a temperature which generally ranges from
about 230.degree. C. to about 350.degree. C., preferably about
250.degree. C. to about 310.degree. C. and, most preferably, about
260.degree. C. to about 290.degree. C. for about 0.1 to about 6
hours, or preferably, for about 0.2 to about 2 hours, until a
polymer having the desired degree of polymerization, as determined
by inherent viscosity, is obtained. The polycondensation step may
be conducted under reduced pressure which ranges from about 53 kPa
(400 torr) to about 0.013 kPa (0.1 torr). Stirring or appropriate
conditions are used in both stages to ensure adequate heat transfer
and surface renewal of the reaction mixture. The reaction rates of
both stages are increased by appropriate catalysts such as, for
example, alkoxy titanium compounds, alkali metal hydroxides and
alcoholates, salts of organic carboxylic acids, alkyl tin
compounds, metal oxides, and the like. A three-stage manufacturing
procedure, similar to that described in U.S. Pat. No. 5,290,631,
may also be used, particularly when a mixed monomer feed of acids
and esters is employed.
[0034] To ensure that the reaction of the diol component and
dicarboxylic acid component by an ester interchange reaction is
driven to completion, it is sometimes desirable to employ about
1.05 to about 2.5 moles of diol component to one mole dicarboxylic
acid component. Persons of skill in the art will understand,
however, that the ratio of diol component to dicarboxylic acid
component is generally determined by the design of the reactor in
which the reaction process occurs.
[0035] In the preparation of cycloaliphatic polyester or polyester
elastomer by direct esterification, i.e., from the acid form of the
dicarboxylic acid component, polyesters are produced by reacting
the dicarboxylic acid or a mixture of dicarboxylic acids with the
diol component or a mixture of diol components and the optional
branching agent component. The reaction is conducted at a pressure
of from about 7 kPa gauge (1 psig) to about 1379 kPa gauge (200
psig), preferably less than 689 kPa (100 psig) to produce a low
molecular weight polyester product having an average degree of
polymerization of from about 1.4 to about 10. The temperatures
employed during the direct esterification reaction typically range
from about 180.degree. C. to about 280.degree. C., more preferably
ranging from about 220.degree. C. to about 270.degree. C. This low
molecular weight polymer may then be polymerized by a
polycondensation reaction.
[0036] The cycloaliphatic polyester and polyester elastomer may
exist as a compatible blend or a miscible blend and may be present
in a broad range of weight percentages based on the total weight of
the article. More than one cycloaliphatic polyester and/or
polyester elastomer may be used as needed to obtain the desired
properties of the shaped article. For example, the shaped article
may comprise about 5 to about 100 weight percent of one or more
cycloaliphatic polyesters and from 0 to about 95 weight percent of
one or more polyester elastomers, based on the total weight of the
article. In another example, the shaped article comprises about 5
to about 95 wt % of one or more cycloaliphatic polyesters and about
5 to about 95 wt % of one or more cycloaliphatic polyester
elastomers. In yet another example, the shaped article may comprise
about 30 to about 100 weight percent cycloaliphatic polyester and 0
to 70 weight percent polyester elastomer. Other examples of weight
percentages of the polyester and polyester elastomer include, but
are not limited to, about 90 to about 100 weight percent
cycloaliphatic polyester and 0 to 10 weight percent polyester
elastomer, and about 30 to about 50 weight percent cycloaliphatic
polyester and 50 to 70 weight percent polyester elastomer.
Additional specific examples of shaped article compositions are
about 10 wt % cycloaliphatic polyester and about 90 wt %
cycloaliphatic polyester elastomer; about 20 wt % cycloaliphatic
polyester and about 80 wt % cycloaliphatic polyester elastomer;
about 60 wt % cycloaliphatic polyester and about 40 wt %
cycloaliphatic polyester elastomer and about 80 wt % cycloaliphatic
polyester, and about 20 wt % cycloaliphatic polyester elastomer;
and about 90 wt % cycloaliphatic polyester and about 10 wt %
cycloaliphatic polyester elastomer.
[0037] In a further example, the shaped article of the instant
invention comprises about 5 to about 95 wt % of poly(1,4
cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate), abbreviated
herein as "PCC", as the cycloaliphatic polyester and about 95 to
about 5 wt % of a polyester elastomer comprising at least 95 mole
%, based on the total moles of diacid residues, of residues of
1,4-cyclohexanedicarboxylic acid; and about 98 to about 70 mole %,
based on the total diol residues, of residues of
1,4-cyclohexanedimethanol. In this embodiment, for example, the
polyester elastomer can comprise poly(1,4 cyclohexylenedimethylene
1,4-cyclohexanedicarboxylate) copolymerized with with about 2 to
about 30 mole % of PTMG having an average molecular weight of about
400 to about 2000 (abbreviated herein as "PCCE"). The polyester
elastomer also may comprise from about 0.1 to about 2 mole %, based
on the total diacid residues, of the residues of a trimellitic acid
or anhydride as a branching agent. PCC has a glass transition
temperature Tg of about 65.degree. C., whereas the polyester
elastomer is a soft elastomer having a Tg below room temperature
(about -20.degree. C.). In oriented films, PCC has a modulus that
is about half that of typical biaxially oriented PET film (e.g.
Mylar.TM.) or fiber, thus giving it a softer feel. The Tg of the
miscible blend will fall roughly linearly between the
cycloaliphatic polyester and the polyester elastomer, because both
polymers have similar structures. The modulus of the article will
also vary with the composition of the article.
[0038] The cycloaliphatic polyesters and cycloaliphatic polyester
elastomers are resistant to chemical and UV attack and impart
additional stiffness and processability in comparison with
substantially linear aliphatic polyesters. Because of this
resistance, the shaped article also will be resistant to UV and
chemical attack over the entire compositional range of
cycloaliphatic polyester and polyester elastomer. Thus, the level
of polyester elastomer can be varied depending on the tactile and
toughness related end-use desired for the article. At high levels
(above about 30 wt %), for example, the polyester elastomer
significantly softens the article to the point that it is flexible
at room temperature and feels similar to an olefin or plasticized
PVC. For example, the combination of PCC and PCCE gives a film that
is softer and tougher than PCC alone, but is more easily processed
and oriented in comparison to PCCE alone. Orientation further
creates a film that can be further thermally stabilized by
heatsetting. Because these polyester compositions may be
strain-crystallized and heatset, the articles can exhibit excellent
properties over a much broader temperature range than other
traditional soft feel resins like plasticized PVC, polyolefins and
the like.
[0039] The shaped articles of the invention may comprise a bottle,
film, sheet, profile, fiber, tube, or molded object and may also
include any standard additives well known to persons skilled in the
art such as, for example, pigments, dyes, slips, antiblocks, chain
extenders, stabilizers, lubricants, flame retardants, electrostatic
pinning agents, nucleators, foaming agents, voiding agents, melt
strength enhancers, antistatic agents, plasticizers, optical
brighteners, compatibilizers, and the like. Although the
cycloaliphatic polyester and, hence, the shaped article, is
inherently stable to UV light, small amount of a hindered amine
light stabilizer (HALS) may be added to the cyclopolyester or to
the composition to scavenge radicals formed during the extrusion
process or by photodegradation initiated from UV absorption by
impurities that may be found in the cycloaliphatic polyester or
polyester elastomer. Examples of HALS that may be used for this
purpose include CHIMMASORB.RTM. 119, CHIMMASORB.RTM. 944,
TINUVIN.RTM. 770, and others available from Ciba Specialty
Chemicals and CYASORB.RTM. UV-3529 and CYASORB.RTM. UV-3346
available from Cytec Industries. HALS are usually used at levels of
0.1 to 1 weight percent. Additionally, some UV absorbing additive
may also be added to the composition if the film is to be used as a
protective layer over another surface. Examples of effective UV
absorbers are: benzophenones such as TINUVIN.RTM. 81, CYASORB.RTM.
UV-9, CYASORB.RTM. UV-24, and CYASORB.RTM. UV-531; benzotriazoles
such as TINUVIN.RTM. 213, TINUVIN.RTM. 234, TINUVIN.RTM. 320,
TINUVIN.RTM. 360, CYASORB.RTM. UV-2337, and CYASORB.RTM. UV-5411;
and triazines such as TINUVIN.RTM. 1577, and CYASORB.RTM. 1164. For
the polyester elastomer, one or more oxidative stabilizers may be
used in some instances to retard the breakdown of any polyester
residues, if present. Examples of stabilizers that may be used for
this purpose include hindered phenyl stabilizers such as
IRGANOX.RTM. 1010 and IRGANOX.RTM. 1076, which are typically used
at levels of about 0.1 to about 1 weight percent.
[0040] The cycloaliphatic polyester and polyester elastomer may be
dry blended or melt mixed in a single or twin screw extruder or in
a Banbury Mixer prior to the preparation of the shaped article. For
example, unoriented shaped articles may be prepared by the
traditional methods such as chill roll casting, calendering, melt
blowing, die extruding, injection molding, spinning, etc. For
example, the high melt strength of the polyester elastomer will
make the calendering of films at lower temperatures easier. Direct
extrusion from the reactor as is common with many fiber operations
is also possible. For example, in a typical procedure for preparing
film, the melt is extruded through a slotted die using melt
temperatures of about 200 to 280.degree. C. and then cast onto a
chill roll at about 20.degree. C. to about 100.degree. C.
(70.degree. F. to 210.degree. F.). The optimal casting temperature
will vary depending on the amount of elastomer in the composition.
The formed film can have a nominal thickness of anywhere from about
5 to 300 mils depending on the final desired thickness of the film
after stretching. Another typical thickness range is 10 to 100
mils.
[0041] The shaped article of the invention may be oriented by
various techniques known to persons skilled in the art and
depending on the nature of the article. For example, film, sheet,
profiles, and tubes may be uniaxially or biaxially stretched using
one or more of the following techniques: machine direction oriented
("MDO") drafting, tentering, double bubble stretching, compression
enhanced stretching, compression molding, solid-state extrusion,
and the like. Bottles and other molded articles may be extrusion or
injection molded and then oriented by stretch blow molding. Fibers
may be uniaxially stretched using similar techniques well known to
persons skilled in the art. Stretching is usually performed at or
near the glass transition temperature Tg, of the polyester. A
typical temperature range for stretching is from about Tg+5.degree.
C. to about Tg+30.degree. C. (Tg+10.degree. F. to Tg+60.degree.
F.); higher stretch temperatures may used for faster stretch rates.
For example, for high speed fiber spinning, the spinning rates are
often high enough that significant orientation can be imparted at
temperatures higher than the above. Stretch ratios are typically
from 2.times. to 5.times.in each direction, although actual stretch
ratios will vary depending on the temperature and stretch rates
involved. Typically for a sequential stretch, as performed with an
inline drafter and tenter, the second stretch is performed at a
slightly hotter temperature (for example, 5.degree. C. to
15.degree. C. above the first stretch). In one embodiment of the
invention, a typical stretch ratio is in the range of 3.times. to
4.times. where strain hardening is optimal.
[0042] The level of orientation in the article can be quantified by
optical birefringence. Birefringence is the difference in
refractive index between any two of the three principal directions
in the material. These directions are the machine direction (MD),
transverse direction (TD) and the thickness direction (ND) for a
film (for a fiber the directions are axial, radial and
circumferential). Thus, there are 3 values of birefringence:
(MD-TD), (TD-thickness) and (MD-thickness) although only two of
these are independent. The birefringence is effectively a measure
of the difference in orientation between these two directions. A
birefringence of zero indicates no difference in orientation
between the respective directions. If all three values of the
birefringence equal zero, then the article is unoriented, as for
example with a cast film.
[0043] The nominal refractive index for the unoriented
cycloaliphatic polymers of the present invention is approximately
1.510 (at a wavelength of 632 nm). For a highly oriented film, the
maximum birefringence is typically about 0.02 to about 0.03. This
low variation in birefringence with these cycloaliphatic polyesters
can be advantageous in optical applications where the in-plane
refractive indices need to be constant in all directions (to
prevent unwanted polarization or distortion). For example, in an
equi-biaxially oriented film, the refractive index in the MD and TD
direction should be the same, while the thickness direction
refractive index will be much lower (due to the relative
orientation). Variations in process, however, will result in slight
variations in the MD and TD refractive indices. For an aromatic
polymer, these variations can be large enough to cause visual
distortions. In contrast, for the film of the present invention,
the difference in MD and TD refractive indices will always remain
small thereby causing fewer distortions.
[0044] Typically, the oriented, shaped articles of the instant
invention have at least one birefringence greater than about 0.005.
In another example, the shaped article of the invention may have at
least one birefringence greater than about 0.01. For most films
(particularly equi-biax), this maximum birefringence will usually
be the (MD-thickness) or (TD-thickness). For fibers, it will
typically be the (axial-radial) birefringence.
[0045] The shaped article may be heatset depending on the end use
requirements. Heatsetting will normally impart thermal stability to
article in order to prevent shrinkage at higher temperatures. It is
accomplished by constraining the shaped article while heating to
temperatures from about 125.degree. C. to 200.degree. C. and is
well known, for example, in the film and fiber industries. Usually
some relaxation is allowed during heatsetting (about 5 to 10%) to
reduce stress in the shaped article. Residence time in the heatset
oven can be as little as a few seconds to a few minutes depending
on oven sizes, line speed, and other factors. Typical heatsetting
temperatures are 170.degree. C. to 210.degree. C. The shaped
articles optionally can then be stretched a second time either in a
two-stage stretch such as, for example, with fibers, or through
"tensilization", for example, with films, to further improve
properties. Typically films that are heatset at 190.degree. C.
(375.degree. F.) are dimensionally stable up to a nominal
temperature of 175.degree. C. (350.degree. F.).
[0046] Shaped articles of the present invention can also be
processed using other techniques well known in the art. For
example, films can be embossed or otherwise engraved using
appropriate compression or casting rolls. Lenticular films for
graphic arts applications are particularly useful with the present
invention where outdoor UV stability or chemical resistance are
required. The lower density articles can produced through the
addition of foaming agents (chemical or gas) or voiding agents. For
example, the shaped article may be a microvoided through by
blending in voiding agents, i.e., small amounts of particles or
incompatible polymers which form voids on stretching. This process
is called "voiding" and may also be referred to as "cavitating" or
"microvoiding". Voids are obtained by incorporating about 5 to
about 50 weight % of small organic or inorganic particles or
"inclusions" (referred in the art as "voiding" or "cavitation"
agents) into a matrix polymer and orienting the polymer by
stretching in at least one direction. During stretching, small
cavities or "microvoids" are formed around the voiding agent. When
voids are introduced into polymer films, the resulting voided film
not only has a lower density than the non-voided film, but also
becomes opaque and develops a paper-like surface. This surface also
has the advantage of increased printability; that is, the surface
is capable of accepting many inks with a substantially greater
capacity over a non-voided film. In either case, the creation of
small voids/holes in the article leads to a lowering of the
density, an increase in the opacity and insulative properties, and
inherent UV blocking without the need of a separate UV absorber
because of the scattering of light by the voids. Microvoided
articles have the added benefit a lower overall film cost and
greater ease separation/recyclability, especially in where such
articles are used in packaging applications such as, for example,
as labels.
[0047] The shaped article also may be a film or sheet and is
understood to include the various embodiments described herein
generally for the shaped articles of invention. Films of the
present invention may be used in a variety of applications such as
protective overlays, laminates, etc. or as standalone structures
for graphic arts. The combined UV and chemical resistance coupled
with toughness and softness makes these films ideal for protective
touchpad covers. The films can be printed or decorated as
needed.
[0048] Films of the present invention are typically lower in
crystallinity than aromatic polyesters like PET and PBT and, thus,
are ideal candidates for "thermoformable BOPET" applications such
as furniture overlaminates. This process refers to biaxially
oriented, crystalline films, typically made from a low to moderate
copolymer modified PET, that still retain some degree of
thermoformability by controlling the type and amount of
crystallinity induced during stretching and heatsetting. In
comparison to PET films, the films of the invention typically have
better chemical and UV resistance, lower crystallinity, and may be
better suited for most applications where thermoformablity of a
crystalline film is desired.
[0049] For example, the shaped article may be a shrink film that is
produced by standard film forming techniques such as extrusions,
blowing, calendering an the like, and oriented by stretching in one
or directions without heatsetting. These films can be used as for
example, food and beverage shrink sleeve labels, package bundling,
tamper evident packing and the like. The film and labels can be
seamed or glued using hot melt adhesives, solvent bonding,
ultrasonic welding, RF sealing, heat sealing, or traditional tapes
and adhesives. In another example, the shaped article may be a
biaxially oriented film that may be a shrink film or may be heatset
to impart dimensional stability. Further, these films may also be
microvoided as described hereinabove.
[0050] The shaped articles of the present invention may comprise
one or more layers and may be formed by known methods such as
coextrusion, coinjection, lamination and ultrasonic staking. Some
examples include multilayer film or sheet, multilayer bottles,
laminated packaging films and bicomponent fibers. The shaped
article may, for example, comprise a plurality of layers, wherein
at least one layer has a thickness of 1 .mu.m or less. In this
embodiment, for example, the shaped article may be a film and,
because of the very low refractive index, can be an excellent
candidate for one of the "microlayers" in iridescent and other
light controlling film technology. In such films, many hundreds of
layers of two alternating, dissimilar layers are coextruded
together using special die technology. The layers are chosen such
that their refractive indices are significantly different, to
maximize internal reflectance and enhance the pearlescent,
iridescent look of the film. The polyesters and polyester
elastomers of the present invention have a very low refractive
index, that can be easily coupled with another polyester having
high refractive index such as, for example, PEN or PET.
[0051] In another embodiment, the shaped article is a fiber which
may be a staple, monofilament, or multifilament fiber having a
shaped cross-section. For the purposes of this invention, the term
"fiber" refers to a shaped polymeric body of high aspect ratio
capable of being formed into two or three dimensional articles such
as woven or nonwoven fabrics. In addition, fiber refers to
filaments that may take any of the various forms well known to
persons skilled in the art, namely monofilaments, multifilaments,
tows, staple or cut fibers, staple yarns, cords, woven, tufted, and
knitted fabrics, nonwoven fabrics, including melt blown fabrics and
spunbond fabrics, and multilayer nonwovens, laminates, and
composites from such fibers. Most fiber forms are heatset. The
fibers of the present invention may be a monofilament,
multifilament, or bicomponent fiber. Our novel fibers may be
produced as a staple, yarn, cord, or a direct spun, nonwoven
fabric.
[0052] Monofilament fibers generally range in size from about 20 to
about 8000 denier per filament (abbreviated herein as "d/f") and
are particularly useful in paper machine clothing applications. The
preferred fibers will have d/f values in the range of about 500 to
about 5000. Such monofilaments may be in the form of unicomponent
or bicomponent fibers. Bicomponent fibers may have sheath/core,
side by side, or other configurations known to persons skilled in
the art. Other multicomponent configurations are also possible. The
process of preparing bicomponent fibers also is well known and is
described in U.S. Pat. No. 3,589,956. In a bicomponent fiber, the
polyester and polyester elastomer of this invention will be present
in amounts of about 10 to about 90 wt. % and will generally be used
in the sheath portion of sheath/core fibers. The other component
may be from a wide range of other polymeric materials including but
not limited to polyesters such as PET, PBT, PTT, polylactides and
the like as well as polyolefins, cellulose esters, and polyamides.
Side by side combinations with significant differences in thermal
shrinkage can be utilized for the development of a spiral crimp. If
crimping is desired, a saw tooth or stuffer box crimp is generally
suitable for many applications. If the second polyester is in the
core of a sheath/core configuration, such a core optionally may be
stabilized.
[0053] For multifilament fibers of our invention, the size may
range from about 2 micrometers for melt blown webs, about 0.5 to
about 50 d/f for staple fibers, and to about 5000 d/f for
monofilament fibers. Multifilament fibers may also be used as
crimped or uncrimped yarns and tows. Fibers used in melt spun and
melt blown web fabric may be produced in microdenier sizes.
[0054] Fibers can similarly be used in a wide range of products
because of the variety in modulus coupled with dimensional
stability. The excellent optics of the fibers make them good
candidates for such applications as light piping and fiber optics
since their refractive index is lower than other aromatic
polyesters.
[0055] In a further embodiment, our invention provides a shaped
article, comprising:
[0056] i. about 30 to 100 weight percent, based on the total weight
of the article, of a cycloaliphatic polyester comprising about 98
to about 100 mole %, based on the total mole % of diacid residues,
of residues of 1,4-cyclohexanedicarboxylic acid; and about 90 to
about 100 mole %, based on the total mole % of diol residues, of
residues of 1,4-cyclohexanedimethanol; and
[0057] ii. 0 to about 70 weight percent of an polyester elastomer
comprising least 90 mole %, based on the total moles of diacid
residues, of the residues of at least one diacid selected from the
group consisting of 1,4-cyclohexanedicarboxylic acid and
terephthalic acid; about 2 to about 30 mole %, based on the total
diol residues, of a poly(tetramethylene ether) glycol having an
average molecular weight of about 400 to about 2000, and about 98
to about 70 mole % of the residues of at least one diol selected
from the group consisting of 1,4-cyclohexanedimethanol and
1,4-butanediol; and about 0.1 to about 2 mole %, based on the total
diacid residues, of the residues of at least one branching agent
selected from the group consisting of trimellitic acid, trimellitic
anhydride, and pyromellitic dianhydride;
[0058] wherein said article is oriented by stretching in at least
one direction.
[0059] The shaped article may include the various embodiments of
the cycloaliphatic polyesters, polyester elastomers, branching
agents, additives, and shaped article forms described hereinabove.
For example, the weight percentages of the polyester and polyester
elastomer may be about 90 to about 100 weight percent
cycloaliphatic polyester and 0 to 10 weight percent polyester
elastomer or, in another example, about 30 to about 50 weight
percent cycloaliphatic polyester and about 50 to about 70 weight
percent polyester elastomer The shaped article may further comprise
one or more hindered amine light stabilizers, UV absorbers, optical
brighteners, or oxidative stabilizers. As described previously, the
shaped article may be a bottle, film, sheet, profile, fiber, tube,
or molded article, and may be heatset. Representative embodiments,
again as described previously, include shrink film, heatset film,
and microvoided film. Each of these films may be monoaxially or
biaxially oriented.
[0060] Our invention further provides a polyester composition
useful for the preparation of shaped articles, comprising:
[0061] i. about 20 to about 80 weight percent, based on the total
weight of the article, of a cycloaliphatic polyester comprising
about 98 to about 100 mole %, based on the total mole % of diacid
residues, of the residues of one or more of diacids selected from
the group consisting of 1,3-cyclohexanedicarboxylic acid and
1,4-cyclohexanedicarboxylic acid; and about 70 to about 100 mole %,
based on the total mole % of diol residues, of the residues of one
or more diols selected from the group consisting of
1,3-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobut-
anediol, and 1,4-cyclohexanedimethanol; and
[0062] ii. about 20 to about 80 weight percent of a polyester
elastomer;
[0063] wherein said composition at 25.degree. C. has a storage
modulus of at least 0.3 GPa and a tan delta of at least 0.02.
[0064] The polyester and polyester elastomer are as described
previously. The polyester composition has a storage modulus of at
least 0.3 gigaPascals ("GPa") and a tan delta of at least 0.02. In
another example, the polyester composition has a tan delta of at
least 0.05 and a storage modulus of at least 0.5 GPa. The term
"storage modulus", as used herein, is well understood by persons
skilled in the art as a measure of the stiffness of the polyester
composition. It is obtained from dynamic mechanical analysis and
represents the "in-phase" component of the modulus for an
oscillatory type loading. For most applications, it is similar in
value to the standard static tensile modulus. Similarly, the term
"tan delta", as used herein, is understood by persons skilled in
the art to be measure of the dampening characteristic of the
material. It represents the ratio of energy dissipated to elastic
energy stored during one oscillation of the polymer under a
sinusoidally applied load. It reflects the extent to which the
composition absorbs energy imparted to the material such as, for
example, sound energy. Materials with high values of tan delta
typically are very useful for noise and sound dampening
applications and for vibration control. Furthermore, articles like
bottles and films made with high tan delta materials are not noisy
and "crinkly" when squeezed. The high tan delta coupled with a high
storage modulus gives the composition a unique and desirable soft
feel that has the proper tactile balance of stiffness and softness,
in addition to low-noise attributes. The article has a desireable
feel like that of plasticized PVC or olefins but with all of the
inherent chemical, thermal and UV resistance of the cycloaliphatic
polymers.
[0065] The composition may include the various embodiments of the
cycloaliphatic polyesters, polyester elastomers, branching agents,
additives, and article forms described hereinabove for the shaped
articles of the invention. For example, the diacid residues may
comprise the residues of 1,4-cyclohexanedicarboxylic acid. In
another example, the diol residues may comprise the residues
1,4-cyclohexanedimethanol. The polyester composition may comprise
about 30 to about 50 weight percent cycloaliphatic polyester and
about 50 to about 70 weight percent polyester elastomer.
[0066] In another embodiment of the invention, the polyester
composition consists essentially of:
[0067] i. about 30 to about 80 weight percent, based on the total
weight of said composition, of a cycloaliphatic polyester
consisting essentially of about 98 to about 100 mole %, based on
the total mole % of diacid residues, of residues of
1,4-cyclohexanedicarboxylic acid; and about 90 to about 100 mole %,
based on the total mole % of diol residues, of residues of
1,4-cyclohexanedimethanol; and
[0068] ii. about 20 to about 70 weight percent of a polyester
elastomer consisting essentially of least 90 mole %, based on the
total moles of diacid residues, of the residues of
1,4-cyclohexanedicarboxylic acid or terephthalic acid; about 2 to
about 30 mole %, based on the total diol residues, of a
poly(tetramethylene ether) glycol having an average molecular
weight of about 400 to about 2000, and about 98 to about 70 mole %
of the residues of 1,4-cyclohexanedimethanol or 1,4-butanediol; and
about 0.1 to about 2 mole %, based on the total diacid or diol
residues, of the residues of trimellitic acid, trimellitic
anhydride, or pyromellitic dianhydride.
[0069] The phrase "consisting essentially of" is used herein is
intended to encompass a polyester composition in which the
cycloaliphatic polyesters comprise primarily
1,4-cyclohexanedicarboxylic acid and 1,4-cyclohexanedimethanol and
is understood to exclude any elements that would substantially
alter the essential properties of the polyester composition to
which the phrase refers. Although the composition of the present
invention is based predominantly on cycloaliphatic polyesters, it
is understand that the article can also contain a small amount of
other non-cycloaliphatic polymers blended therein, as long as the
general properties are not significantly affected. These other
polymers may include one or more of such polymers as
polycarbonates, polyesters, polylactic acid, polyhydroxybutyrate,
polyhydroxyvalerate, cellulosics, olefins, styrenics, acrylics,
acetals, nylons, starches, and there copolymers. These blend
components may be added intentionally, as in the case of a
microvoiding agent, or unintentionally as is the case of
regrind/recycle of multilayer articles. For example, one embodiment
of the polyester composition of the invention can include of one or
more of: hindered amine light stabilizers, UV absorbers, optical
brighteners, oxidative stabilizers or other additives which do not
substantially alter the physical properties of soft feel,
flexibility, toughness, clarity, UV, and/or chemical resistance as
described previously. In another example, the addition of another
polymer to the polyester composition at a level which would be
expected to alter substantially the flexibility of the polyester
composition would be excluded from the invention. In yet a further
example, polyester compositions are intended to be excluded if a
substantial amount of a polycarbonate is present such that the UV
resistance and chemical resistance of the polyester composition is
materially affected. The following discussion provides examples of
the kinds of modifications that may be employed, but those of skill
in the art will readily recognize others.
[0070] Shaped articles such as, for example, bottles, films,
sheets, profiles, fibers, tubes, and molded objects, may be
prepared from the polyester compositions of instant invention as
described previously. The shaped article may further comprise one
or more hindered amine light stabilizers, UV absorbers, optical
brighteners, or oxidative stabilizers. As described previously, the
shaped article may be heatset. Representative embodiments, again as
described previously, include shrink film, heatset film, and
microvoided film. Each of these films may be monoaxially or
biaxially oriented. The shaped articles also may comprise one or
more layers and may be formed by known methods such as coextrusion,
coinjection, lamination and ultrasonic staking. Some examples
include multilayer film or sheet, multilayer bottles, laminated
packaging films and bicomponent fibers. The shaped article may, for
example, comprise a plurality of layers, wherein at least one layer
has a thickness of 1 .mu.m or less. As previously noted, such
articles, because of their very low refractive index, can be an
excellent candidate for one of the "microlayers" in iridescent and
other light controlling technology.
[0071] Our invention further provides a process for a polyester
composition, comprising mixing:
[0072] i. about 20 to about 80 weight percent, based on the total
weight of the composition, of a cycloaliphatic polyester comprising
about 98 to about 100 mole %, based on the total mole % of diacid
residues, of the residues of one or more diacids selected from the
group consisting of 1,3-cyclohexanedicarboxylic acid and
1,4-cyclohexanedicarboxylic acid; and about 70 to about 100 mole %,
based on the total mole % of diol residues, of the residues of one
or more diols selected from the group consisting of
1,3-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobut-
anediol, and 1,4-cyclohexanedimethanol; and
[0073] ii. about 20 to about 80 weight percent of an polyester
elastomer;
[0074] wherein the composition at 25.degree. C. has a storage
modulus of at least 0.3 GPa and a tan delta of at least 0.02. The
polyester composition is understood to include the various
embodiments of the cycloaliphatic polyesters, polyester elastomers,
branching agents, and additives as described hereinabove. The
process may be carried out using any means of efficiently mixing
the cycloaliphatic polyester and polyester elastomer known to
persons of ordinary skill in the art such as, for example, by using
a single screw extruder. Alternatively, mixing may be accomplished
using a high shear device such as, for example, a twin screw
extruder or Banbury Mixer.
[0075] The following examples further describe and illustrate the
invention.
EXAMPLES
[0076] General--Test methods followed standard ASTM procedures
wherever possible. Because of the small size of some of the samples
stretched on the T.M. Long film stretcher, however, some minor
modifications to the ASTM procedures were required.
[0077] Tensile properties were measured by ASTM Method D882. Tear
properties were measured by ASTM D1938. Tensile heat distortion
temperature (THDT) was measured by applying a 0.345 MPa load to a
piece of film with a 1 inch (25.4 mm) gauge length and then heating
from room temperature at approximately 2.degree. C./minute. The
temperature at which the film exceeds 2% strain is denoted as the
"tensile heat distortion temperature".
[0078] Total light transmittance and haze were measured by ASTM
Method D1003. Refractive index was measured using a Metricon.TM.
prism coupler with a 633 nm wavelength laser or obtained from the
literature. Values were measured in all three principal directions
(i.e. machine direction, transverse direction and thickness
direction) and birefringences calculated for each combination (i.e.
MD-TD, MD-thickness, TD-thickness, etc.).
[0079] Melting points and glass transition temperatures were
determined by either DSC (using ASTM Method D3418) or more
typically by dynamic mechanical analysis (16 rad/s freq). Storage
modulus and tan delta values were obtained at room temperature
(25.degree. C.) for each of the samples described in Table IV.
[0080] Other test methods are described within the examples as
appropriate.
Examples 1-9
[0081] Preparation of Cast Films and Properties--Pellet/pellet
blends of (A) cycloaliphatic polyester (poly(1,4
cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) and (B)
Eastman PCCE elastomer (poly(1,4 cyclohexylenedimethylene
1,4-cyclohexanedicarboxylate) copolymerized with 0.75 mole %
trimellitic anhydride and 8 mole % poly(tetramethylene glycol)
having an average molecular weight of 1000) were extruded on a 1"
Killion extruder at 260.degree. C. (500.degree. F.) and cast into
16 mil thick film. Blend levels ranged from neat A to neat B and
various combinations in between (see Table I). It was found that
casting onto the chrome chill roll was easily accomplished with all
films except for neat B due to the excessive sticking. Addition of
only 5% of component A (95% B) eliminated the sticking problem and
made the film easy to handle, with low haze and few surface
defects.
[0082] Samples of the cast films were then tested and the data
compiled in Table I. All films had minimal orientation. For
example, Example 1 had refractive indices of 1.5065, 1.5062, and
1.5059 in the MD, thickness and TD directions respectively. The
maximum birefringence is found in the MD-TD direction and is 0.0006
(calculated as 1.5065 minus 1.5059). For the elastomer blend
Example #5, the refractive indices were 1.5123, 1.5098 and 1.5108
in the MD, thickness and TD directions respectively. Maximum
birefringence was 0.0025 in the MD-thickness direction. This
elastomer blend was slightly higher than the glassy Example 1, most
likely because the more rubbery texture allowed for some stretching
between die and casting roll. Nevertheless, the birefringence is
still essentially negligible for Example 5 (and all of the cast
films).
[0083] Tg values were obtained by dynamic mechanical measurement
and refer to the onset temperature of the transition. For the
elastomers (Examples 6 through 9), the glass transitions were very
broad due to the morphological nature of the soft segments.
Otherwise the Tg was found to decrease systematically with
increasing wt % of B as expected. For B amounts greater than about
70%, the Tg decreases to below room temperature and the film feels
more pliable like a plasticized vinyl.
[0084] Moduli similarly dropped with increasing B with Example 9
(neat B) being about 1/4 of the modulus of neat A (Example 1). Tear
resistance, while being somewhat dependent on film direction--MD
being the machine direction and TD being the transverse
direction--was still found to be higher for higher levels of B.
This is expected since the elastomer imparts toughness to the
film.
1TABLE I Cast Film Properties Example # 1 2 3 4 5 6 7 8 9 % (B) 0%
5% 10% 20% 40% 80% 90% 95% 100% Tg (onset, deg C.) 65.9 58.6 58
45.2 33.6 -10 -17 -20 -20 % Haze 0.17 0.13 0.63 0.13 0.46 0.22 0.23
0.36 1.34 Thickness [in] 0.0156 0.0152 0.0177 0.0165 0.0167 0.0168
0.016 0.0154 0.014 Transmittance 92.9 93.0 92.8 92.8 92.5 92.4 92.3
90.8 91.1 Tear Resistance [lb/in]- 285.0 344.8 333.5 400.5 423.0
447.3 396.0 348.8 243.8 MD Tear Resistance [lb/in]- 278.6 312.3
328.2 389.3 456.0 509.0 466.9 466.3 562.5 TD MD Break Strain [%]
424 423 451 475 474 642 664 629 479 MD Break Stress [psi] 5400 5072
5196 5056 4612 4921 5008 5079 7237 MD Modulus [psi] 120607 117219
120666 117788 90189 35388 32573 26137 36268 TD Break Strain [%] 401
414 442 459 513 688 682 712 751 TD Break Stress [psi] 5237 4943
5200 5103 4921 5002 4376 4387 4191 TD Modulus [psi] 121946 119810
122316 118898 94541 35373 31719 30399 36301
Examples 10-19
[0085] Film Stretching and Heatsetting--Examples 1 through 5 (i.e.
up to about 40% elastomer) were biaxially stretched 3.5.times.3.5
and 4.times.4 on a T.M. Long Film.RTM. stretcher to give the films
of Examples 10-14. The stretch temperature was taken to be
approximately 10.degree. C. (18.degree. F.) above the blend Tg
listed in Table I. Because the Examples above Example 5 had a Tg
below room temperature, they were not included in this particular
example due to temperature control issues (although they are to be
included in a later experiment). Some of the oriented films were
further modified by heatsetting at 190.degree. C. (375.degree. F.)
for 1 minute using a constraining frame, in order to impart thermal
stability. Properties for the non-heatset films are described in
Table II. The heatset films are tabulated in Table III.
[0086] The refractive indices for Example 10 were 1.5274, 1.5232
and 1.5026 in the MD, TD and thickness direction respectively.
Because it is equi-biaxially oriented, the MD and TD refractive
indices are approximately the same. The maximum birefringence is
0.025 (MD-thickness). Actual birefringences did not vary
significantly with elastomer content as long as the film was
stretched at the proper temperature relative to Tg. For the
elastomer modified Example 15, the refractive indices were 1.5259,
1.5262 and 1.5010 in the MD, TD and thickness directions
respectively. Maximum birefringence was again 0.025 which is the
same as with Example 10. Similar values were observed for all of
the oriented blends, regardless of elastomer content.
[0087] It was observed that stretching to 4.times.4 was possible
for all but the cast film of Example 1. The films of Examples 2
through 5 could be stretched to 4.times.4 but were more prone to
tearing, thus they are not included further in this example. It
should be noted however, that stretching to higher levels could be
achieved easily by raising the stretch temperature. For comparative
purposes, a nominal biaxially oriented and heatset PET film has a
modulus in each direction of approximately 400,000 to 500,000 psi,
or about twice that of Example 10 (or Example 15).
[0088] Increasing levels of B reduce this even further to a modulus
value about 1/3 that of PET. Thus the films of the current
invention have a much softer feel. Tear resistance of PET tends to
be lower than the values quoted but it varies considerably due to
variations in IV, additive orientation level, etc. A nominal value
is around 20 to 30 lb/in. This is equivalent to the heatset samples
containing pure A, and better than films containing 5 to 20% B.
However, at B=40%, the tear resistance is almost twice as high as
the PET and will increase further with increasing B.
[0089] PET haze values are typically from 1 to 5% depending on the
degree of antiblock, regrind, etc. but this is still higher than
the films described herein. Upper use temperatures for heatset PET
film are typically quoted at 150.degree. C. (300.degree. F.)
although values as high as 210.degree. C. (410.degree. F.) can be
obtained depending on the allowable shrinkage. The films of the
present invention were thermally stable up to a nominal 175.degree.
C. (350.degree. F.) based on the tensile heat distortion
temperature (THDT) data in Table III. Thus the films/fibers of the
present invention can be used in essentially the same temperature
range as many traditional aromatic polyesters.
[0090] PET films, typically, are prone to UV attack and most often
require some type of UV protecting cap layer in order to survive
outdoor applications. Otherwise they tend to rapidly discolor and
turn brittle. The films of the present invention however, do not
show any signs of discoloration or property loss when exposed to
the same conditions and can survive for much longer periods of
time.
2TABLE II Non-Heatset Biaxially Oriented Film Properties (3.5
.times. 3.5 .times. Stretch) Example # 10 11 12 13 14 wt % B 0 5 10
20 40 Thickness [in] 0.0017 0.0014 0.0015 0.0015 0.0015 % Haze 0.09
0.31 0.13 0.13 0.42 Transmittance 92.7 92.7 92.6 92.3 92.4 MD Break
Strain [%] 74.0 83.0 54.8 82.9 95.8 MD BreakStress [psi] 17738
12210 12377 15336 11757 MD Modulus [psi] 185835 124987 151249
143230 119936 TD Break Strain [%] 63.3 80.5 59.7 85.4 104.4 TD
BreakStress [psi] 21056 13771 23007 18840 16092 TD Modulus [psi]
221816 152753 279484 197279 162548
[0091]
3TABLE III Heatset Properties of Biaxially Oriented Films Example #
15 16 17 18 19 Wt % B 0 5 10 20 40 Thickness [in] 0.0017 0.0014
0.0015 0.0015 0.0015 % Haze 0.77 0.13 0.13 0.17 0.59 Transmittance
92.46 92.36 92.6 92.35 92.19 MD Break Strain [%] 105 96 129 114 109
MD BreakStress [psi] 16760 16725 16490 16341 14774 MD Modulus [psi]
203292 191833 179824 169908 121638 TD Break Strain [%] 99 109 106
127 99 TD BreakStress [psi] 17778 16136 15707 14321 14524 TD
Modulus [psi] 203180 180257 167101 161177 126136 MD THDT (deg C.)
175.4 186.5 186.2 171.0 184.4 TD THDT (deg C.) 185.0 175.8 185.3
178.9 174.9 TearResistance MD (lb/inch) 32.0 10.4 5.2 9.0 61.8
TearResistance TD (lb/inch) 24.7 10.9 10.2 6.0 35.5
Example 20
[0092] Dynamic Mechanical Comparison of Films--Originally it was
anticipated that films containing between about 50 and 80% B would
be too difficult to handle and/or would be of no practical benefit.
As a result, these blends were not made in the first trial (hence
their absence in Table I through III). Nevertheless, because of the
unique soft feel that was observed in the intermediate blends
(Examples 4, 5, and 6), it was decided to produce an additional
film (Example 20) containing 65 wt % of component B. This film (and
similar films in this compositional range) had a feel and texture
similar to plasticized PVC, but without the negative environmental
aspects.
[0093] Dynamic mechanical analysis was performed on the unoriented
blends to better understand the unique properties, Table IV lists
the storage modulus E', and tan delta at room temperature for
Examples 1-9 and Example 20. It is observed that the modulus drops
from about 0.9 GPa to about 0.25 GPa as the blend transitions from
pure A to pure B. This is typical of a transition from a glassy
polymer (A) to an elastomer (B). In contras, tan delta increases
from about 0.01 for pure A, to 0.15 for pure B. Tan delta a measure
of the viscous damping of the polymer and is effectively the amount
of energy dissipated as heat per cycle of "vibration". Glassy
polymers like pure A, have very low damping and thus low values of
tan delta.
[0094] For a film to have the desired "plasticized" feel similar to
flexible PVC, the damping should be as high as possible, but the
film also has to have a certain degree of stiffness, or it will
feel more like a viscous liquid than a dampened solid. The samples
containing from about 20% B up to those containing about 80% B were
consistent with the desired soft, pliable feel. This corresponds to
values of modulus greater than about 0.3 GPa and tan delta greater
than about 0.02.
4TABLE IV Dynamic Mechanical Data Example# Wt % B E' (GPa) tan
.delta. Film Texture 1 0 0.82 0.014 Stiff/glassy 2 5 0.94 0.006
Stiff/glassy 3 10 0.89 0.012 Stiff/glassy 4 20 0.90 0.021
Stiff/pliable 5 40 0.82 0.056 Pliable 20 65 0.59 0.103 Pliable 6 80
0.30 0.149 Soft/pliable 7 90 0.22 0.133 Soft/Rubbery 9 100 0.28
0.148 Soft/Rubbery
Examples 21 and 22
[0095] Continuous Biaxial Orientation--Biaxially oriented films
were produced on a continuous film line consisting of an MDO
drafter and a tenter frame using pure cycloaliphatic polyester A
(Example 21) and a 40/60 blend of A and B (Example 22). The latter
was a "soft feel" blend based on the results of the previous
example. Both films contained 0.2 wt % silica antiblock, 0.3 wt %
HALS stabilizer (CYASORB.RTM. 3529), 0.25 wt % of WESTON.RTM. 619
organophosphite, and 0.5 wt % of UV absorber (CYASORB.RTM. 1164).
Example 22 also contained 0.1 wt % of an antioxidant. These
additives were in concentrate form, and added using gravimetric
feeders.
[0096] Cast films (18 mils thick) were produced on a 2 inch Davis
Standard extruder at 260-275.degree. C. (500-530.degree. F.). The
films were then sequentially oriented by first stretching in the
machine or axial direction using a drafter, followed by stretching
in the transverse direction using a tenter frame. Linespeed
entering the drafter was 17.9 fpm (feet per minute) and leaving the
fast draw roll was 53.7 fpm resulting in a draw ratio of 3. The
preheat and draw roll temperatures of the drafter were both
75.degree. C. for Example 21 but were set close to room temperature
for Example 22. Annealing and cool down rolls were set at 37 C.
After drafting, the film was sent through the tenter frame where
the film was stretched 3.5.times. in the transverse direction using
a preheat and anneal temperature of 80.degree. C. for Example 21.
The heatset zone was set at 190.degree. C. with a 5% clip
retraction to improve dimensional stability. For Example 22, the
preheat and stretch temperature were set cold (close to room
temperature) followed by a similar heatset at 190.degree. C. Both
films were tough and dimensionally stable to temperatures of
180.degree. C.
Examples 23-32
[0097] Weathering Data Pellet/pellet blends of (A) cycloaliphatic
polyester poly(1,4 cyclohexylenedimethylene
1,4-cyclohexanedicarboxylate) and (B) Eastman PCCE elastomer were
extruded on a 2" Davis Standard extruder at 260-275.degree. C.
(500-530.degree. F.) and cast into 20 mil thick film. The blends
also contained various additives summarized in Table IV including a
microcrystalline silica antiblock agent (AB), an antioxidant (AO)
Irganox 1010, a hindered amine light stabilizer (HALS) CYASORB.RTM.
3529, a organophosphite (P) WESTON.RTM. 619, and an ultraviolet
light absorber (UVA) CYASORB.RTM. 1164. The films were subsequently
biaxially stretched 3.times.3 on a T.M. Long Film.RTM. stretcher.
The stretch temperature was taken to be approximately 75.degree. C.
for Examples 23-25 and 50.degree. C. for Examples 26-32. Some of
the oriented films were further modified by heatsetting at
190.degree. C. (375.degree. F.) for 1 minute using a constraining
frame, in order to impart thermal stability.
[0098] The films were exposed to ultraviolet light using an Atlas
Ci65 weathering device according to the ASTM G155 test method using
the cycle 1 method. Specifically, the weathering procedure utilized
a Xenon lamp, borosilicate inner and outer filters, an irradiance
of 0.35 W/m.sup.2/nm at 340 nm, a black panel temperature of
63.degree. C., relative humidity of 55%, and an all light cycle
with 18 minutes of water spray every 120 minutes. The total
exposure time was 2000 kJ. The key responses were change in color
(.DELTA.YI), loss in total light transmission (.DELTA.LT), and time
to embrittlement (Failure). Failure was determined using a
90.degree. bend. The sample failed if any cracks were observed or
the sample broke.
[0099] PET films, typically, are prone to UV attack and most often
require some sort of UV protecting cap layer using expensive UVA in
order to survive outdoor applications. Otherwise they tend to
rapidly discolor and turn brittle. The films of the present
invention however, do not show significant discoloration and
require only a low loading of inexpensive HALS to prevent property
loss when exposed to the same conditions and can survive for much
longer periods of time.
5TABLE V Weathering Example 23 24 25 26 27 28 29 30 31 32 B (%) 0 0
0 50 50 50 50 50 65 75 AB (%) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2
0.2 AO (%) 0.1 0.1 0.1 0.1 0.1 HALS (%) 0.3 0.3 0.3 0.3 0.3 0.3 0.3
P (%) 0.25 0.25 0.25 0.25 UVA (%) 0.5 0.5 0.5 0.5 Cast Films
.DELTA.YI 0.1 -0.9 0.5 -2.0 -1.2 -1.0 -0.5 0.6 .DELTA.LT (%) -0.9
-0.4 -2.9 -0.8 0.4 -0.3 -0.4 -0.4 Failure (kJ) 360 >2000
>2000 184 1450 >2000 >2000 >2000 >2000 >2000
Oriented Films .DELTA.YI 0.15 0.41 -0.21 -0.41 0.20 .DELTA.LT (%)
-2.3 -2.2 -0.4 -0.8 -0.9 Failure (kJ) 725 >2000 >2000 360 360
>2000 >2000 >200
Example 33 and Comparative Examples 1-3
[0100] Chemical Resistance Testing--Chemical resistance testing was
performed on cycloaliphatic polyester A, and compared with PETG
(Eastman 6763, containing 31 mole % 1,4-cyclohexanedimethanol,
Comparative Example 1), polycarbonate (MAKROLON 2608, Bayer
Corporation, Comparative Example 2) and acrylic (PLEXIGLAS DR-101,
Comparative Example 3). In particular, the critical strain at which
environmental stress cracking occurs for a range of different
solvents, was determined for each sample. Testing was performed on
injection molded bars ({fraction (1/8)} inch thick, unoriented)
rather than oriented film because of the difficulty in determining
critical strain on a flexible thin film. It is noted that the
oriented film samples are expected to show even better chemical
resistance due to the presence of stabilizing crystallinity.
[0101] Actual testing involves flexing the bar over a Bergen
elliptical strain jig with constantly varying curvature, so as to
apply different strain levels at different points of the bar.
Solvent is applied in the form of a filter pad on the surface of
the flexed bar, left for 10 minutes, and the critical strain
determined where stress cracking begins to occur. These values are
reported in Table V for a range of solvents. As observed, many
solvents like toluene, acetone, rubbing alcohol, and MEK did not
stress crack the cycloaliphatic polymer within the strain range of
the test. Compare this with the other polymers where stress
cracking occurred at very small strains (e.g. toluene and acetone).
With the exception of iso-octane and chloroform, the cycloaliphatic
polyester had as good, or better chemical resistance than the
Comparative Examples. Furthermore, PETG, PC, and acrylic are all
polymers which do not undergo strain crystallization, so
orientation will not improve their chemical resistance (as opposed
to the cycloaliphatic polymer which will improve).
6TABLE V Chemical Resistance and Critical Strain at Stress Cracking
Example No. Solvent 33 C1 C2 C3 Iso-octane 0.42 1.28 >1.7 1.17
Heptane 0.56 0.77 1.2 1.13 Toluene >1.7 <0.33 <0.33 0.46
Acetone >1.7 <0.33 <0.33 0.32 i-propanol 1.39 0.44 >1.7
0.41 Rubbing Alcohol >1.7 0.61 >1.7 NT MEK >1.7 <0.33
<0.33 NT Ethyl Acetate 1.7 <0.33 <0.33 0.32 Chloroform
dissolved <0.33 <0.33 NT
Example 34
[0102] Spinning of Fiber--As-spun (undrawn) fibers were extruded
with polyester A described in Example 1, at 10 denier per filament.
Resin was dried 8 hours at 60.degree. C. prior to spinning. A
spinneret with 10 holes and with a 0.3 mm diameter hole size was
used to produce the fibers. Extrusion conditions were as follows:
Zone 1: 165.degree. C., Zone 2: 220.degree. C., Zone 3: 240.degree.
C., Zone 4: 240.degree. C., Zone 5: 250.degree. C., Zone 6:
260.degree. C., Zone 7: 270.degree. C. and Zone 8: 270.degree.
C.
[0103] The extruded fibers were passed over 2 godet rolls traveling
at 1000 m/m and then collected on a winder with a speed of 1000
m/m. A fiber spinning lubricant (LK 5572E20) was added to the fiber
during extrusion.
[0104] This fiber was then oriented on a towline. The following
conditions were used to orient and heatset the fiber: feed yarn
denier: .about.10, filaments/pkg: 10, number of packages in creel:
5, water bath temperature: 70.degree. C., steam tube temperature
-160.degree. C. The first roll speed was set at 20 m/min, the
second roll was at 45 m/min, and the 3rd roll was at 68 m/min. HT
roll speed and temperature was 68 m/min and 150.degree. C.
respectively. The resulting draw ratio was 3.4. The drafted fiber
had a denier/filament of approximately 3 and overall was of good
strength and appearance.
Example 35
[0105] Blow Molding of Bottles--Preforms were injection molded
using the cycloaliphatic polyester A described in Example 1.
Molding was performed on a Boy 22, laboratory injection molding
machine using a standard 20 oz. bottle mold. Resin was predried at
55.degree. C. overnight prior to processing.
[0106] The nominal processing temperature for the resin was
260.degree. C., with a mold temperature set at 4.degree. C.
(38.degree. F.). Cooling time in the mold was 10 seconds resulting
in an overall cycle time of 30 seconds. Injection hold pressure was
1400 psig with a nominal injection pressure of 60 psig.
[0107] Bottles were blown from the molded performs using a
laboratory reheat blow molding machine. The heating station
utilized 5 quartz heaters set at rheostat settings of 131, 132,
135, 90 and 90 (from top of perform to finish area respectively).
Reheat time was 77 seconds, with a blow time of 5 s, a soak time of
16 s, and a blow delay time of 1.5 seconds. The stretch rod
pressure was 50 psig, and the blow pressure was 140 psig. Resulting
bottles had excellent clarity/aesthetics and toughness compared to
a normal PET bottle. Furthermore they were lighter in weight due to
the lower density of the resin.
Example 36
[0108] Production of Shrink Film--A uniaxially shrinking film was
produced using cycloaliphatic polyester A by stretching 3.5.times.
on a tenter frame. Preheat and stretch temperatures were set at
80.degree. C. with the anneal zone temperature set at 60.degree. C.
(this is in contrast to Example 21 where the anneal zone was set to
190.degree. C. to heatset the film). The linespeed was 35 fpm.
After stretching, a 10 cm by 10 cm sample was immersed in a hot
water bath set at 95.degree. C. for 10 seconds. The shrinkage in
the stretch direction was 3 cm or 30% relative to the original
length. The refractive indices were 1.5259, 1.5274 and 1.5016 in
the TD, MD and thickness directions respectively. The maximum
birefringence (TD-thickness) was 0.024.
[0109] If desired, even higher shrinkages can be obtained by
stretching the film more (e.g. 4.times. instead of 3.5.times.)
stretching at a colder temperature (e.g. 75.degree. C.), or
incorporating comonomers into the polymer (e.g. 10 mole % neopentyl
glycol) to reduce strain induced crystallinity (and thereby
increase shrinkability).
Example 37
[0110] Production of Microvoided Film--In this prophetic example,
cycloaliphatic polyester A is pellet/pellet blended with 15 wt % of
polypropylene (used as a microvoiding agent). The film is extruded
as described in Example 20 with the polypropylene dispersed within
the polyester and having a particle size distribution ranging from
about 1 to 50 um. The film is then sent through a tenter frame and
stretched 3.5.times. at 80.degree. C. to induce microvoids into the
film. The resulting microvoids are predicted to make the film
opaque and lower in density. The film is then heatset at
190.degree. C. to make it dimensionally stable at higher use
temperatures.
Example 38
[0111] Production of Iridescent Light Controlling Film--In this
prophetic example, the cycloaliphatic polyester A is coextruded
with PET to form a film with many alternating layers (i.e.
cycloaliphatic/PET/cycloaliphatic- /PET, etc.). Extrusion
conditions for the cycloaliphatic polyester are described in
Example 1. PET is extruded using a nominal 280.degree. C. melt
temperature, with the die temperature decreased to approximately
250.degree. C. to better match with the cycloaliphatic. The
polymers are brought together into a feedblock/manfold designed to
create a multitude of alternating layers. For the present example,
51 equal thickness layers are created with the cycloaliphatic as
the cap on the outside surfaces (for chemical resistance) and
otherwise alternating with the PET layers. The initial cast film is
250 microns. This film is then biaxially oriented 3.times. in both
the machine and transverse direction at a nominal stretch
temperature of 90.degree. C. This results in an oriented film with
a final thickness of 28 microns. Thus, each layer is predicted to
be approximately 0.54 microns in thickness. The refractive index of
the cycloaliphatic polymer is expected to not change much and is
predicted to be nominally 1.51 in both the MD and TD, whereas the
PET refractive index is predicted to be of the order of 1.66 in
each direction.
[0112] Because of the high refractive index mismatch between
layers, there will be considerable reflection at each interface.
Furthermore, because the final individual layer thickness is the
same as the wavelength of visible light, there will be considerable
optical interference effects resulting in specular variations in
the reflected and transmitted light. Hence the iridescent effect.
At longer wavelengths, particularly those in the infrared at
approximately 2 um, the the individual layers will be approximately
{fraction (1/4)} of a wavelength thick and will therefore serve as
very efficient reflectors of this infrared energy.
[0113] As an alternate approach, the above film can be uniaxially
oriented resulting in different refractive indices for each layer,
in each direction. For example, with a 4.times.1 stretch, the PET
layer is predicted to have approximately a 1.66 refractive index in
the stretch direction, versus a 1.56 refractive index in the
non-stretch direction. The cycloaliphatic refractive indices will
not change appreciably and will be assumed to be about 1.51 in each
direction. If the cast film is adjusted to be 100 microns
initially, the final thickness after a 4.times.1 stretch is
predicted to be 25 microns or 0.5 microns per layer (again in the
range of visible light). In contrast to the previous example, the
refractive index mismatch is predicted to be higher in the stretch
direction than the nonstretch direction, so the percentage of
reflected light will be higher in this direction (particularly at
wavelengths that are about 4.times. higher than the layer
thickness). Thus, light waves polarized parallel to the stretch
direction is expected to undergo more reflection than those
polarized perpendicular. The net effect is that the film
effectively serves as a type of polarizer, preferentially letting
only certain light wave orientations through. Other variations of
the above examples can be easily envisioned by simply increasing
the number of layers (greater reflectivity), or changing the layer
thickness (different wavelengths reflected).
* * * * *